An abrupt increase of bills is however not envisaged, website Dariknews.bg quoted DKEVR head Boyan Boev as saying.

Price hikes might be introduced on a quarterly basis, a measure already applied for natural gas, heating, and hot water.

Boev underscored any changes could be avoided only if Brussels responded properly to a complaint DKEVR lodged Wednesday regarding state aid granted to two US-owned thermal power plants and to renewable energy producers.

So far the EU Commission has not provided an official answer.

The energy watchdog also suggests that prices for purchasing electricity from the two TPPs be reduced and that the quota of renewable energy bought to be pumped into the system be curtailed.